Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae

Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly slow rotation of most white dwarf stars.     

Engineering Systems Thinking: A Multifunctional Definition

This paper asks what engineering systems thinking is and seeks to determine what distinguishes it from systems thinking. The purpose of the study was to identify the characteristics of engineers who are able to think in the manner we call engineering systems thinking. The study seeks to define the term engineering systems thinking on a theoretical level and then to move from the theoretical level to the operational level. A thorough understanding of engineering systems thinking on both the theoretical and operational levels will prove useful in the design of curricula to improve and develop thinking of this sort. Our study was based on 28 interviews, 14 lectures, and 2 observation sites. This paper treats only the material that pertains directly to engineering systems thinking.     

Factors affecting high-frequency fungal protoplast fusion

Summary Factors influencing the fusion frequency of protoplasts have been examined with auxotrophic mutants ofAspergillus nidulans. The optimum conditions were a total of 5 to 15 million protoplasts per ml, and 25% polyethylene glycol (PEG) 4000 or 6000 as fusogenic agent in 10 to 100 mM CaCl₂ solution.     

Feinstruktur von Pilzzellen. 1. Septen beiPenicillium brevi-compactum

Summary In the centre of the septum between phialide and mutula of certain imperfect penicillia a plug was observed as electron dense mechanism. This observation is rather similar to that ofMoore in the case of 2 Ascomycetes. The author believes these plugs are nuclei migrating through septa. This is because they are not enclosed by the endoplasmatic reticula.     

The nucleocytoplasmic distribution of 3-0-methylglucose in the amphibian oocyte

Summary Ultra-low temperature microdissection was employed to determine the in situ nucleocytoplasmic distribution 3-0-methylglucose in the amphibian oocyte. The nucleocytoplasmic partition ratio, K_n/c, for this non-metabolizable monosaccharide was 1.54±0.08. The observed asymmetry could be explained by the differential solubility of the solute in the water of the nucleoplasm and the cytoplasm.Supported in part by an N.I.H. General Research Support grant to the George Washington University Medical Center.Acknowledgments. The author wishes to thank Mr T. Poandl for skillful technical assistance.     

Three-dimensional architecture of the calcium channel/foot structure of sarcoplasmic reticulum

The calcium channel responsible for the release of Ca2+ from the sarcoplasmic reticulum of skeletal muscle during excitation-contraction coupling has recently been identified and purified. The isolated calcium channel has been identified morphologically with the 'foot' structures which are associated with the junctional face membrane of the terminal cisternae of sarcoplasmic reticulum. In situ, the foot structure extends across the gap of the triad junction from the terminal cisternae of the reticulum to the transverse tubule. We describe here the three-dimensional architecture (3.7 nm resolution) of the calcium channel/foot structure from fast-twitch rabbit skeletal muscle, which we determined from electron micrographs of isolated, non-crystalline structures that had been tilted in the electron microscope. The reconstruction reveals two different faces and an internal structure in which stain accumulates at several interconnected locations, which could empty into the junctional gap of the triad junction. The detailed architecture of the channel complex is relevant to understanding both the physical path followed by calcium ions during excitation-contraction coupling and the association of the terminal cisternae and the transverse tubules in the triad junction.     

2,3-二氯苯基哌嗪合成方法的改进

2,3-二氯苯胺硫酸盐经重氮化,再与KI置换生成相应的芳基碘化物,产率81%.芳基碘化物与哌嗪在二甲基亚砜中反应,CuI和脯氨酸为催化剂,收率20%.该方法操作简单,对湿不敏感，产物易于分离，具有一定的实用价值。